Cold rolling lubrication



United States Patent "ice 3,390,084 COLD ROLLING LUBRICATION AlanWainwright Lake, Banstead, Surrey, England, assignor to Henry W. Peabody(Industrial) Limited N0 Drawing. Filed July 1, 1966, Ser. No. 562,121 19Claims. (Cl. 252--34.7)

This invention is concerned with the cold rolling of ferrous andnon-ferrous metals.

In the cold rolling of metal (this operation most commonly being appliedto steel, aluminium, copper and brass), metal stock in the form of sheetor strip is passed between pairs of metal work rolls to which pressureis applied to reduce the thickness of the metal to a desired value. Thework rolls are commonly supported by backup rolls of greater diameter inorder to resist distortion of the work rolls by bending. In such metalrolling operations, it is necessary to apply a lubricant at theinterface between the rolls and the metal. This lubricant serves tomaintain a suitable coefiicient of friction between the metal stock andthe work rolls in order to ensure, in turn, the desired rate ofdeformation of the metal and to prevent the transfer of metal to therolls themselves by frictional pick up with consequent damage to thesurface of the metal being rolled. Lubrication is also necessary in thearc of contact between the work rolls and the backup rolls. Thelubricant also serves as a coolant to dissipate the heat produced bydeformation of the metal stock and to control thermal distortion of therolls and thus ensuring a satisfactory surface finish and flatness forthe rolled metal.

The rolling lubricants customarily used in metal rolling operations areoil-in-water emulsions of varying degrees of stability and crudedispersions of oil in water maintained by mechanical agitation and theselubricants are subject to a number of disadvantages. During operationthe lubricant is continuously circulated from a conveniently locatedreservoir to sprays or nozzles from which it is sprayed into the rollgaps and, in some cases, also on to the rolls and the lubricant thendrains from the mill stands and is returned to the reservoir. Thelubricant returning back into the reservoir carries with it metaldetritus and scale formed or removed from the rolled material duringrolling and it is difficult to remove this suspended material from thelubricant owing to the inherent difficulty of effectively filtering anemulsion or crude dispersion, which difiiculty is enhanced by the factthat partial separation of the oil and water phases usually takes placeduring the actual rolling operations and in the reservoir. Due to suchphase separation, the lubricating properties of the lubricant aredeleteriously affected and skimming of the liquid in the reservoir toremove the separated oil phase is required.

It has hitherto been thought desirable that separation of the oil andwater phases of such emulsions or crude dispersions should take place atthe metal-roll interface in order that the optimum lubricatingproperties of the lubricant should be attained and various attempts havebeen made to overcome the problems posed by the persistance of suchphase separation in the reservoir to which the lubricant is returned.Thus it has been proposed to use a lubricant composition which forms astable emulsion only at a temperature below that attained at themetal-roll interface (which is the maximum temperature encounteredduring circulation of the lubricant) and it has been proposed to use alubricant composition which forms a stable aqueous solution only at atemperature below that attained at the metal-roll interface. Theseproposals necessitate careful control of the temperature of thelubricant during the operation of the mill in order to ensure that thelubricant has cooled in the reservoir to a temperature at which thestable emulsion or solu- 3,300,084 Patented June 25, 1968 tion isreformed before it is returned to the mill via the sprays.

We have now found that the existence of separated oil and water phasesat the roll-metal interface is not necessary in order to obtain goodlubrication in the cold rolling of metals and we have developed atemperature stable, dilute aqueous solution of certain organic compoundswhich is an excellent metal rolling lubricant and from which none of theconstituents separate at any temperature encountered in the circulationof the lubricant during cold rolling operations.

In accordance with the present invention, therefore, we provide a methodof cold rolling metals, in which the roll-metal interface is lubricatedwith a circulating lubricating composition which is a dilute aqueoussolution of a blend of (a) from 40 to by weight of a salt formed betweenat least one amine which is non-volatile at ambient temperatures and asynthetic or naturally occurring fatty acid containing at least 12carbon atoms, a fatty acid distillation residue or a syntheticpolymerised fatty acid, (b) 0.1 to 20% by weight of a polyoxyalkyleneoxide condensate of a fatty acid or rosin acid, a sorbitan ester of afatty acid containing at least 12 carbon atoms, a fatty aciddistillation residue or a synthetic polymerised fatty acid, or apolyoxyalkylene condensate of such a sorbitan ester, (c) 5 to 50% byweight of a synthetic fatty acid alkyl ester, the fatty acid containingat least 12 carbon atoms and the alkyl group containing up to 4 carbonatoms, and (d) 0 to 50% by weight of a watersoluble bactericide.

In contrast to the oil-in-water emulsions or crude dispersions which arecurrently used as mill lubricants, the foregoing aqueous compositionsare solutions which are stable against any separation of one or moreconstituents thereof at all temperatures from slightly above thefreezing point of the solution to the boiling point thereof. Thesolutions are, therefore, stable against separation of any constituentthereof, other than water by evaporation, under all the temperatureconditions that are present in a cold rolling operation. The optimumtemperature for any particular rolling operation can, therefore, beselected with no limitation being imposed by the mill lubricantemployed.

Since the solutions remain stable, they can be filtered using filteringmeans capable of separating the finest suspended particles and can becentrifuged using the highest speeds in order to remove suspended metaland scale particles (arising from the rolling operation) therefromwithout significant loss of the active ingredients from the solution.Suspended droplets of any extraneous oil, arising from leakage ofmechanical or hydraulic. systems, which may be present in the solution,are also removed by such filtration or centrifugation.

While the stability of the aqueous solution lubricants againstseparation of the constituents at elevated temperatures is theirprincipal advantage, they also possess the further advantage that theygive an excellent balance of lubricating and cooling properties for awide range of reductions. In the cold rolling of steel, it is necessaryto use a lubricant having high lubricity when carrying out a heavyreduction, that is a reducion in excess of 60%, for example in theproduction of thin sheet gauges (plate having a thickness of less than0.024 inch) and to use a lubricant having a low lubricity when carryingout a light reduction, that is a reduction of less than 60%, for examplein the production of thick sheet gauges (plate having a thicknessgreater than 0.024 inch).

The problems of changing from one lubricant to another on the rollingmill when the type of product rolled is being changed, are considerable.The aqueous solution lubricants used according to the present invention,however, give excellent results with a wide range of reductions and canbe used without any variation in their composition for the production ofsheet steel products ranging in thickness from tinplate gauge (typically0.008 inch), through the light and medium sheet gauges (typically lessthan 0.024 inch and greater than 0.024 inch respectively) up to theheavy sheet gauges (typically up to 0.075 inch).

A further advantage of the aqueous solution lubricants is that thetraces thereof which are left on the material after the cold rollingoperation are completely volatilised during annealing or other heattreatment carried out after cold rolling so that products withexceptionally clean surfaces are obtained.

Pickled hot band steel intended for subsequent cold rolling using suchan aqueous solution lubricant is preferably coated at the finishing endof the pickle line with a similar solution which is dried on the steelsurface by means of the drying equipment normally provided on suchlines. The pickled hot band steel is coiled for storage pen-ding coldrolling and the dried film atfords excellent protection against rustingand minimises the risk of internal scratching within the coil due torelative movement of contact surfaces whilst handling. The dried film ofthe lubricant also provides lubrication for the first rolling pass inthe mill.

The aqueous solution lubricants can also be used as the mill lubricantin the cold rolling of hot band steel that has been coated with aconventional mineral and/ or fatty oil composition as protectivelubricant; this situation can arise, for example, where hot bandmaterial coated with a conventional composition comes from an outsidesource for subsequent cold rolling. The presence of such conventionalmineral and/or fatty oil compositions on the material subjected to coldrolling normally has no deleterious effects on the aqueous solutionlubricants provided that proper steps are taken to remove excess oilfrom the mill lubricant system, for example, by filtration, centrifugingor regular skimming.

The amine salt constituent of the lubricant composition used accordingto the invention preferably contains a small excess of amine, forexample a 5 excess. Suitable amines include, for example, mono-, diandtri-ethanolamine, mixed isopropanolamine and aminomethylpropanol;methylamine, ethylamine, diethylamine and morpholine are unsuitablesince they are too volatile at ambient temperatures. The long chainfatty acid present in the amine salt may, for example, be oleic orstearic acid. Alternatively, the acid component of the amine salt can bea residue from the distillation of fatty acids, which residue maycontain polymerised fatty acids, such as pitch acids, or can be such apolymerised fatty acid, particularly oleic acid dimer or trimer, alone.The amine salt can, of course, be formed from a mixture of such acidcomponents.

The polyoxyalkylene oxide condensate constituent of the lubricantcomposition is preferably a polyoxyethylene oxide condensate and thecondensate is preferably one derived from the condensation of from 4 to44 moles of the alkylene oxide with one mole of fatty or rosin acid;such condensates will, in general, have a molecular weight in the rangeof from 400 to 600. Examples of suitable condensates are those obtainedby the condensation of 8 moles of ethylene oxide with 1 mole of crudetall oil fatty acids; of 9 moles of ethylene oxide with 1 mole ofstearic acid; and of 22 moles of ethylene oxide with 1 mole of oleicacid. The polyoxyalkylene oxide condensate used should not be one thathas a negative solubility coefiicient in water. Instead of apolyoxyalkylene oxide condensate of a fatty or rosin acid, a sorbitanester or polyoxyalkylene sorbitan ester, such as sorbitan monooleate orpolyoxyethylene moles) sorbitan monopalmitate can, as indicated above,be used.

As indicated above, the synthetic fatty acid alkyl ester employed is onederived from a fatty acid containing at least 12 carbon atoms and thealkyl group of which contains up to 4 carbon atoms. These fatty acidalkyl esters are completely peptised in the micellar structure of theamine salt so that even though some of the alkyl esters have onlylimited solubility in water on their own, when present in the lubricantcompositions they are effectively .solubilised. These synthetic fattyacid alkyl esters act as anti-foaming agents. It is preferred to use:fatty acid butyl esters, particularly butyl stearate.

Where the lubricant composition contains a watersoluble bactericide, thelatter should be a compound which does not deleteriously affect thewater-solubility of the other constituents of the composition. Suitablewater-soluble bactericides are, for example, ortho-phenyl-phenol, amylcresol, catechol, and 2-hydroxymethyl-2-nitro-propanediol, of which thefirst is preferred.

in order that the invention may be more fully understood, the followingexamples, in which the proportions are by volume, are given by way ofillustration only.

EXAMPLE 1 A mixture of the following composition was formed by blendingthe components at 140 F.:

Percent Triethanolamine 25 Oleic acid A 2% solution of this blend inwater was used as the mill lubricant on a Schloemann mill rolling mirrorfinish steel strip. The strip was rolled at 1500 feet/minute to obtainan overall reduction of in three passes.

The same operation was also carried out using a conventional 5%oil-in-water emulsion lubricant.

The overall reduction of 90% was obtained with lower loads and the finalproduct also had a better surface finish when the aqueous solutionlubricant was used than when the emulsion lubricant was used.

When using the 2% solution lubricant, the lubricant circulation systemremained cleaner and lasted six times longer than the emulsion lubricantbefore it had to be discarded. There was no separation of anyconstituent of the lubricant solution at any point in the circulation ofthe solution from the reservoir to the mill stand and from the latterback to the reservoir.

EXAMPLE 2 A mixture of the following composition was formed by blendingthe components at F.:

A 2% aqueous solution of this blend was used as the mill lubricant on awide 4-stand tandem mill rolling mild steel strip. With this lubricant,overall reductions of up to 84% were obtained at high speed with lowermill loads and Wth the production of a cleaner product than with aconventional crude oil-in-water dispersion lubricant that had previouslybeen used on the same mill in rolling the same product. The mill androlls remained significantly cleaner than had formerly been the case.

Gauges ranging from 0.010 to 0.060 inch were satisfactorily rolled usingthe same 2% aqueous solution, that is without any alteration in thelubricant composition.

The used 2% solution was allowed to remain static for several weeks andwhen again brought into service, there were no indications of theunpleasant odours normally associated with bacterial contamination anddevelopment. The cleanliness of the rolled material was found to beexceptionally good upon final inspection.

EXAMPLE 3 A mixture of the following composition was formed by blendingthe components at 140 F.:

5 98% of the blend of Example 2 2% of ortho-phenyl-phenol.

A 2% aqueous solution of this composition was found to be an exceilentcold rolling lubricant. The bactericide, ortho-phenyl-phenol, has beenfound to afford protection against bacterial growth during the prolongedlife possible with the lubricant composition described.

I claim:

1. In a method of cold rolling metals, in which the roll-metal interfaceis lubricated with a circulating lubricating composition, theimprovement comprising using as said circulating lubricating compositiona dilute aqueous solution of a blend of (a) from 4-0 to 95% by weight ofa salt formed between (i) at least one amine which is non-volatile atambient temperatures and (ii) an acid selected from the group consistingof fatty acids containing at least 12 carbon atoms, fatty aciddistillation residues, and synthetic polymerised fatty acids;

(b) 0.1 to 20% by weight of a surfactant selected from the groupconsisting of (i) polyoxyalkylene oxide condensates of an acid selectedfrom the group consisting of fatty acids and rosin acids,

(ii) sorbitan esters of an acid selected from the group consisting offatty acids containing at least 12 carbon atoms, fatty acid distillationresidues, and synthetic polymerised fatty acids, and

(iii) polyoxyalkylene condensates of said sorbitan esters (ii);

(c) 5 to 50% by weight of a synthetic fatty acid alkyl ester, the fattyacid containing at least 12 carbon atoms and the alkyl group containingup to 4 carbon atoms; and

(d) to by weight of a water-soluble bactericide; none of theconstituents of the blend being emulsified in said solution and none ofthem separating from the solution at any of the temperatures encounteredin the cold rolling and in the circulation of the solution during thecold rolling.

2. A method according to claim 1, in which said aqueous solutioncontains 0.5 to by Weight of said blend.

3. A method according to claim 1, in which said aqueous solutioncontains 1 to 4% by weight of said blend.

4. A method according to claim 1, in which said polyoxyalkylene oxidecondensate (b) (i) is derived from the condensation of from 4 to 44moles of the alkylene oxide with 1 mole of said acid.

5. A method according to claim 1, in which said polyoxyalkylene oxidecondensate (b) (i) is derived from the condensation of 8 moles ofethylene oxide with 1 mole of crude tall oil fatty acids.

6. A method according to claim 1, in which said polyoxyalkylene oxidecondensate (b) (i) is derived from the condensation of 9 moles ofethylene oxide with 1 mole of stearic acid.

7. A method according to claim 1, in which said polyoxyalkylene oxidecondensate (b) (i) is derived from the condensation of 22 moles ofethylene oxide with 1 mole of oleic acid.

8. A method according to claim 1, in which said bactericide (d) isortho-phenyl-phenol.

9. A method according to claim 1, in which said amine salt (2.) containsa small excess of amine.

10. A method according to claim 9, in which the' from the groupconsisting of oleic acid, stearic acid, pitch acids, a synthetic fattyacid dimer and a synthetic fatty acid trimer.

12. A method according to claim 1, in which said sorbitan ester (b)(ii)is sorbitan mono-oleate.

13. A method according to claim 1, in which said polyoxyalkylenesorbitan ester (b)(iii) is polyoxyethylcue-glycol sorbitanmonopalmitate.

14. A method according to claim 1, in which the metal that is rolled ispickled hot band steel and in which a dilute aqueous solution asspecified in claim 1 is applied to the pickled hot band steel and thendried to leave a film of said blend on the steel, prior to effectingcold rolling.

15. In a method of cold rolling steel, in which the roll-metal interfaceis lubricated with a circulating lubrieating composition, theimprovement comprising using as said circulating lubricating compositiona dilute aqueous solution of a blend of (i) about 70% by volume of thesalt formed between triethanolamine and oleic acid;

(ii) about 7.5% by volume of an 8:1 molar condensate of ethylene oxideand crude tall oil fatty acids, and

(iii) about 22.5% by volume of butyl stearate; none of the constituentsof the blend being emulsified in said solution and none of themseparating from the solution at any of the temperatures encountered inthe cold rolling and in the circulation of the solution during the coldrolling.

16. A method according to claim 15, in which said aqueous solutioncontains from 1 to 4% by volume of said blend.

17. In a method of cold rolling steel wherein the rollmetal interface islubricated with a circulating lubricating composition, the improvementcomprising using as said circulating lubricating composition a diluteaqueous solution of a blend of (i) about 70% by volume of the saltformed between triethanolamine and a mixture of equal parts of oleicacid and pitch acids,

(ii) about 7.5% by volume of sorbitan mono-oleate;

and

(iii) about 22.5% by volume of butyl stearate; none of the constituentsof the blend being emulsified in said solution and none of themseparating from the solution at any of the temperatures encountered inthe cold rolling and in the circulation of the solution during the coldrolling.

18. A method according to claim 17, wherein said blend additionallycontains 2% by volume of the total blend of ortho-phenyl-phenol.

19. A method according to claim 17, wherein said aqueous solutioncontains from 1 to 4% by volume of said blend.

References Cited UNITED STATES PATENTS 2,298,432 10/ 1942 Thompson25249.5 2,345,199 3/1944 Hodson 252-347 2,349,585 5/1944 Bond et al.252-358 2,825,693 3/ 8 Beaubien et al 252-49.3 3,296,129 1/ 1967Scheidker et al. 252-495 XR 3,311,557 3/1967 Schiermcier et a1. 252-493XR FOREIGN PATENTS 519,983 12/ 1955 Canada.

561,488 8/ 1958 Canada.

988,073 4/ 1965 Great Britain.

DANIEL E. WYMAN, Primary Examiner.

C. F. DEES, W. H. CANNON, Assistant Examiners.

1. IN A ROLLED METHOD OF COLD ROLLING METALS, IN WHICH THE ROLL-METALINTERFACE IS LUBRICATED WITH A CIRCULATING LUBRICATING COMPOSITION, THEIMPROVEMENT COMPRISING USING AS SAID CIRCULATING LUBRICATING COMPOSITIONA DILUTE AQUEOUS SOLUTION OF A BLEND OF (A) FROM 40 TO 95% BY WEIGHT OFA SALT FORMED BETWEEN (I) AT LEAST ONE AMINE WHICH IS NON-VOLATILE ATAMBIENT TEMPERATURE AND (II) AN ACID SELECTED FROM THE GROUP CONSISTINGOF FATTY ACIDS CONTAINING AT LEAST 12 CARBON ATOMS, FATTY ACIDDISTILLATION RESIDUES, AND SYNTHETIC POLYMERISED FATTY ACIDS; (B) 0.1 TO20% BY WEIGHT OF A SURFACTANT SELECTED FROM THE GROUP CONSISITNG OF (I)POLYOXYALKYLENE OXIDE CONDENSATES OF AN AICD SELECTED FROM THE GROUPCONSISTING OF FATTY ACIDS AND ROSIN ACIDS, (II) SORBITAN ESTERS OF ANACID SELECTED FROM THE GROUP CONSISTING OF FATTY ACIDS CONTAINING ATLEAST 12 CARBON ATOMS, FATTY ACID DISTILLATION RESIDUES, AND SYNTHETICPOLYMERISED FATTY ACIDS, AND (III) POLYOXYALKYLENE CONDENSATES OF SAIDSORBITAN ESTERS (II); (C) 5 TO 50% BY WEIGHT OF A SYNTHETIC FATTY ACIDALKYL ESTER, THE FATTY ACID CONTAINING AT LEAST 12 CARBON ATOMS AND THEALKYL GROUP CONTAINING UP TO 4 CARBON ATOMS; AND (D) 0 TO 5% BY WEIGHTOF A WATER SOLUBLE BACTERICIDE; NONE OF THE CONSTITUENTS OF THE BLENDBEING EMULSIFIED IN SAID SOLUTION AND NONE OF THEM SEPARATING FROM THESOLUTION AT ANY OF THE TEMPERATURES ENCOUNTERED IN THE COLD ROLLING ANDIN THE CIRCULATION OF THE SOLUTION DURING THE COLD ROLLING.